Partner Reported Opportunities (PROs) PRO Fact Sheet No. 203 for Reducing Methane Emissions 

Pipe Glycol Dehydrator to Vapor 

Recovery Unit 

Technology/Practice Overview 

Description 

Glycol dehydration units use electric or

gas assist pumps to re-circulate the lean 

(dry) glycol back to the gas contactor. 

Gas assist pumps are driven by

expansion of the high-pressure gas

entrained in the rich (wet) glycol. This 

methane gas is either vented to the 

atmosphere with water vapor that is 

boiled off in the glycol regenerator, or 

recovered for beneficial use with a flash 

tank separator. 

When flash tank separators and other

vents are piped to a vapor recovery unit

(VRU), more gas can be recovered and 

less methane, volatile organic

compounds (VOC), and hazardous air 

pollutants (HAP) vented from the 

reboiler. The VRU boosts the recovered 

gas pressure enough to inject it into a

fuel gas system, compressor suction, or 

gathering/sales line. 

Operating Requirements 

For full benefit from this practice, the 

existing VRU should have sufficient 

capacity to capture the maximum 

production tank 

simultaneously with 

dehydrator vent load. 

vapor

the 

load 

glycol 

Applicability 

There are no limitations when the VRU 

discharges to a sales line or compressor 

suction. However, where the beneficial 

outlet is a fuel gas system, fuel usage 

may limit the amount of methane 

recovery. 

Methane Emissions 

With sufficient spare capacity in an

existing production tank VRU, all of the 

gas collected by a glycol dehydrator flash 

Estimated 

Gas Price 

Annual 

Methane 

Savings 

Value of 

Annual

 Gas Savings* 

Estimated 

Implementation 

Cost 

Incremental 

Operating Cost 

Payback 

(months) 

$7.00/Mcf 790 Mcf $5,900 $2,000 $100—$1,000 4 - 7 

$5.00/Mcf 790 Mcf $4,200 $2,000 $100—$1,000 6 - 9 

$3.00/Mcf 790 Mcf $2,500 $2,000 $100—$1,000 10 - 15 

Economic and Environmental Benefits 

Economic Evaluation 

Additional Benefits 

 Depending on existing dehydrator system setup, could avoid emissions of HAPs and VOCs 

 Could reduce fuel costs for the dehydrator system or the site by recovering gas that can be used as fuel 

Estimated annual methane emission reductions 790 Mcf per dehydrator unit 

Methane Savings 

* Whole gas savings are calculated using a conversion factor of 94% methane in pipeline quality natural gas. 

Compressors/Engines 

Dehydrators 

Directed Inspection & 

Maintenance 

Pipelines 

Pneumatics/Controls 

Tanks 

Valves 

Wells 

Other 

Applicable Sector(s) 

Production 

Processing 

Transmission 

Distribution 

Other Related Documents: 

Reroute Glycol Skimmer Gas, 

PRO No. 201 

Convert Gas-Driven Chemical 

Pumps, PRO No. 202 

Optimize Glycol Circulation and 

Install Flash Tank Separators in 

Dehydrators, Lessons Learned 

Replacing Gas-Assisted Glycol 

Pumps with Electric Pumps, 

Lessons Learned 
 

 

 

 

 

 

 

PRO Fact Sheet No. 203 Continued 

Pipe Glycol Dehydrator to Vapor Recovery Unit (Cont’d) 

tank separator can be recovered. A dehydrator with

either an electric or energy exchange circulation pump

can recover 300 scf or 900 scf of methane per MMcf of gas

processed, respectively when there is no flash tank 

separator. This is because, when using either a piston or

gear type “energy-exchange” pump, for every unit-volume 

of gas absorbed in the rich TEG leaving the contactor,

two more unit-volumes of gas must be added from wet

feed gas to supply enough power in the driver for the lean 

TEG pump. 

Methane emissions reductions of 7,600 Mcf per year can 

be achieved for a 20 MMcf per day dehydrator having a 

vent condenser, without a flash tank separator, 

circulating 300 gallons of glycol per hour with an energy

exchange pump. The absence of a flash tank separator

(as is common with some International Natural Gas 

STAR Partners) would result in greater emissions and, 

by extension, a greater amount of gas possibly being 

recovered through this practice. 

Economic Analysis 

Basis for Costs and Savings 

Typical methane emissions reductions of 790 Mcf per

year apply to a 20 MMcf per day glycol dehydration unit, 

with an energy exchange pump and flash tank separator

connected to an existing production tank VRU. 

The cost of this project would include planning, design, 

and implementation by an engineer and installation of 

additional piping. Using expert judgment and 

rudimentary estimates of equipment capital and 

installation costs, the implementation costs are 

estimated to be approximately $2,000. Additional 

operating costs are estimated using a cost of 7.5¢ per 

kWh, electrical power cost would be about $340 per MMcf 

per year of gas recovered. 

Discussion 

This technology has a quick payback. The low cost of 

installing the piping connection between the VRU and 

flash tank separator vent and the incremental electrical 

power cost of the vapor recovery compressor partially

offset the value of gas savings. 

EPA provides the suggested methane emissions estimating methods contained 

in this document as a tool to develop basic methane emissions estimates only. 

As regulatory reporting demands a higher-level of accuracy, the methane emission estimating methods and terminology contained in this document may not 

conform to the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W 

methods or those in other EPA regulations. 

The average methane content of natural gas varies by natural gas 

industry sector. The Natural Gas STAR Program assumes the 

following methane content of natural gas when estimating 

methane savings for Partner Reported Opportunities. 

Production 79 % 

Processing 87 % 

Transmission and Distribution 94 % 

Methane Content of Natural Gas 

2011 2